1. Field of the Invention
The present disclosure pertains to methods for rapid detection and identification of microorganisms. More particularly, the disclosure relates to identification of prokaryotic organisms through molecular characterization of their genetic materials, such as DNA or RNA.
2. Description of Related Art
Microorganisms, such as bacteria, are a major cause of infections in higher mammals, including human. Although some infections may be treated without knowing the identity of the infectious agent, it is sometimes important for clinicians to know the identity of the infectious agent in order to prescribe the most effective treatment for the infection. This is particularly true for bacterial infections because different species of bacteria may respond differently to the same antibiotics.
In addition to their role as pathogens, prokaryotic microorganisms also play an important role in many industrial areas. Beer spoilage caused by bacteria has been a chronic problem for the beer industry. Prokaryotes are often found in various environmental contamination sites, and knowledge of the identity of these organisms can be useful for remediation. Identification of these prokaryotes may be instrumental for solving these problems.
Conventional methods for classification and identification of a microorganism require culturing of the microorganism, and typically rely on morphological or biochemical characteristics of the organism. The culturing step may delay identification, which can have consequences on the effectiveness of appropriate treatment, and may also increase exposure of laboratory workers to pathogens. The delay in identification may in turn increase the chances that the pathogens may be spread to others while awaiting lab test results. Moreover, the test results may be skewed when multiple microorganisms are present and the growth of one microorganisms inhibits the growth of others in the laboratory environment. There is therefore a need for a method which may rapidly identify the organisms without requiring culturing of the microorganisms in a laboratory environment.
Nucleic acid sequences of homologous genes have been used to distinguish different species. The differences in nucleotide usage, frequency and arrangement may indicate the degree to which different organisms have diverged from a common ancestor. U.S. Pat. No. 5,849,492 discloses a method for rapid identification of species based on taxonomically variable set of orthologous sequences, including ribosomal RNA genes. More specifically, the '492 patent teaches a process whereby the sequences of ribosomal RNA molecules may be used to identify genetic differences between species. An information theory-based sequence analysis is used to select sequences in the homologous 16S ribosomal RNA genes (16S rDNA) for DNA amplification. The '492 patent discloses a pair of primers amplifying orthologous ribosomal gene or RNA sequences that are selected using information theory-based methods that detect gene regions revealing sequences that are maximally divergent among multiple species, which make these primers and amplicons useful for identifying prokaryotes. However, there are limitations to the sensitivity and specificity of this method, because computational analysis in the '492 patent was based on a multiple alignment of 16S rDNA sequences from only 55 prokaryotic organisms.